1. Technical Field
The present invention relates to a PCB and a method of manufacturing the same.
2. Description of the Related Art
As electronic devices become increasingly smaller, lighter and faster, the circuit patterns of printed circuit boards are required to be denser.
In the past, after an Ajinomoto Build-up film (ABF) is laminated and is desmeared for the purpose of forming roughness in order to improve the adhesive strength between a plated layer and the ABF, a fine circuit is formed by an additive way using electroless plating or electrolytic plating.
However, when rigidity is required but warpage may occur, the ABF is not usable and prepreg should be used instead. If the prepreg is used as a laminate, roughness cannot be formed by desmearing. To overcome this problem, a circuit is formed by laminating a copper foil and the prepreg together and etching the copper foil. However, such a method is limited in forming a fine pattern as compared with the method using the ABF.
Conventionally, a method according to FIGS. 1 through 5 has been used to form a fine pattern.
In order to form a fine pattern on an insulation layer 12, such as the prepreg on which a fine pattern is difficult to be formed, a plate member 11 has been used in the past as shown in FIG. 1, which consists of a copper foil 111 and a thin film resin layer 112 on which roughness cannot be formed thereon. The thin film resin layer 112 is laminated on the copper foil 111. When the plate member 11 is laminated on the insulation layer 12 and the copper foil is removed, the thin film resin layer 112 performs a function of transferring the roughness of the copper foil 111 to the thin film resin layer 112. Accordingly, the copper foil 111 having coarse roughness causes the roughness transferred to the thin film resin layer 112 to be increased such that it is possible to obtain sufficient adhesive strength between the thin film resin layer 112 and the plated layer formed by electroless plating and electrolytic plating in accordance with the additive way. However, as described below, there arises a serious problem of getting core-copper foils 131 and 133 damaged.
The method of forming a fine pattern is as follows. As shown in FIGS. 1 through 5, the plate member 11, the insulation layer 12 and a copper clad laminate 13 having a circuit formed therein are successively laminated and pressed, and then are shaped as shown in FIG. 2. Subsequently, a through-hole 14 is formed as shown in FIG. 3. As shown in FIG. 4, the through-hole 14 is desmeared without removing the copper foil 111 in order to protect the thin film resin layer 112. If the desmear process is performed after removing the copper foil 111, the thin film resin layer 112 is exposed to a desmear solution and damaged. As a result, since the roughness formed on the thin film resin layer 112 is reduced, there occurs a problem in the adhesive strength.
As shown in FIG. 5, the copper foil 111 is removed. In this case, there is a serious problem that etching solution is leaked into the through-hole 14, and then the inner copper foils 131 and 133 are damaged. Consequently, by using the plate member 11 having the laminated thin film resin layer 112 which cannot have roughness, a fine pattern can be formed on the insulation layer 12 on which a fine pattern is difficult to be formed, but the core-copper foils 131 and 133 are damaged.